Yazidi, also commonly spelled Yezidi, is an ancient Kurdish-based religion with historic links to Zoroastrianism, which was founded in what is now Iran. The sect has developed into a separate religion over the centuries: Modern Yazidi recognize a supreme being responsible for creating the Earth, which is overseen by seven angels, according to Christine Allison, a professor of Arab and Islamic Studies at Exeter University in England and author of "The Yezidi Oral Tradition in Iraqi Kurdistan." The Yazidi have friendly ties to Christianity and recognize Jesus as one of the great prophets, according to the Yazidi reference site Yezidi Truth. The Mashaf Reš, or Black Book, one of Yazidi's two main holy books, teaches that the most important of the holy angels, Malak Taus, refused to bow down to Adam — making him an infidel in the eyes of some strict Muslims. The sect has been targeted by the Islamic State of Iraq and al-Sham, or ISIS, which has launched a campaign to "purify" Iraq and neighboring countries of non-Islamist influences.